The separation of fluid mixtures by rectification is one of the largest chemical processes in use. These systems are designed with an economical view toward capital costs relative to operating costs. With the present shortage of energy and the accompanying high cost, however, the necessity of more efficient separation processes is apparent. With this need in mind, the improved efficiency afforded by the disclosed system is the most significant consideration. Other important desirable characteristics are the avoidance of compressor seals, and smaller required components, mainly the re-boiler heat exchanger and reflex condenser. The avoidance of compressor-turbine seals is also a significant consideration as these seals are a perpetual maintenance problem. Generally, the present invention represents a substantial improvement with regard to these considerations.